Angiography imaging modality and intravascular ultrasound (IVUS) imaging modality devices are both used to assess condition of patient blood vessels and each type of device has respective features and advantages. Known systems that use both these types of imaging modality device concurrently require that a location of an IVUS transducer be detected in live angiography images acquired during retraction (pullback) of an IVUS device from a vessel, for example. An intravascular ultrasound (IVUS) medical imaging modality device uses a catheter with a miniaturized ultrasound probe attached to a distal end of the catheter. The proximal end of the catheter is attached to computerized ultrasound equipment. An IVUS device acquires an image inside a blood vessel through a surrounding blood column and the images show the endothelium (inner wall) of the blood vessel in living individuals. An acquired image is mapped to an angiographic X-ray image that was acquired in the presence of contrast agent to allow visualization of vasculature. In order to visualize an artery or vein, an angiographic method is used involving positioning a soft and pliable tip of a guidewire, usually 0.36 mm (0.014″) diameter and about 200 cm long. The guidewire is steered from outside the body, through angiography catheters and guided into a blood vessel branch to be imaged. The ultrasound catheter tip is slid in over the guidewire and positioned, using angiography techniques so that the tip is at the farthest away position to be imaged. Sound waves emitted from the catheter tip are usually in the 10-20 MHz range, and the catheter receives and conducts return echo information to external computerized ultrasound equipment. The equipment constructs and displays real time ultrasound images of a thin section of the blood vessel currently surrounding the catheter tip at a typical 30 frames per second rate. The guide wire is kept stationary and the ultrasound catheter tip is slid backwards, usually under motorized control at a pullback speed of 0.5 min/s, for example.
The detected trajectory of the ultrasound catheter tip as it is slid backwards is prone to error which shows as anatomic mismatch and mis-alignment between an angiographic X-ray image and an IVUS imaging dataset. This is because there may be significant motion during pullback of the ultrasound catheter tip (e.g., cardiac or breathing motion) and there is also no contrast agent present during pullback leading to an absence of landmarks in the X-ray image that would support location of an ultrasound transducer in a vessel. A system according to invention principles addresses these deficiencies and related problems.